biermann@ww.tu-freiberg.de Abstract. A novel steel-based composite material, composed of metastable austenitic stainless steel as matrix and up to 15 % zirconia as reinforcement, is processed by two powder metallurgy routes. The matrix exhibits the so-called TRIP-effect (TRIP: TRansformationInduced Plasticity) and shows a deformation-induced formation of martensite. Compression tests of rod samples processed by cold isostatic pressing show increased strength compared to the non-reinforced steel matrix up to 20 % strain. Three-point bending tests show, however, reduced ductility for high zirconia contents. Filigree honeycomb structures were produced by a novel extrusion technique with extraordinary high values of specific energy absorption. IntroductionMost Metal-Matrix-Composites (MMCs) have a light-metal matrix such as aluminum or magnesium. MMCs with a steel matrix, however, have not been examined very much up to now, although they may be possible candidates for use as high strength and wear resistant materials [1,2].The combination of a steel matrix which shows the TRIP effect (TRIP: Transformation-Induced Plasticity) with a metastable ZrO 2 -reinforcement also exhibiting a martensitic phase transformation was until now only investigated by the group of Guo et al. with regard to the mechanical properties. The studied composite was produced by the conventional powder metallurgical route and hot pressing [3][4][5]. Guo et al. thus created TRIP-steel matrix composites with reinforcements made of yttriapartially stabilized zirconia-particles (2Y-PSZ) and obtained an extraordinary high strength in high deformation rate compression experiments.In the present work results of a new collaborative research center with the title "TRIP-MatrixComposites -design of tough, transformation reinforced composite materials and structures on FeZrO 2 -basis" are presented. Samples of the steel-matrix composite materials were produced by coldisostatic pressing and a novel extrusion technique which is used conventionally in ceramic technology. First results of a variant of the family of composite materials to be developed were already presented in very recent papers [6][7][8].

Metal matrix composites (MMC) containing TRIP‐steel/Mg‐PSZ were processed by cold pressing and conventional sintering in different atmospheres. The MMC was based on austenitic steel in the system Fe‐Cr‐Mn‐Ni showing transformation induced plasticity (TRIP). Depending on the sintering temperature, the sintering atmosphere and the steel composition the phase compositions of MgO partially stabilized zirconia (Mg‐PSZ) were analysed by scanning electron microscopy (SEM), energy dispersive X‐ray microanalysis (EDX) as well as electron backscatter diffraction (EBSD). The interactions between the alloying elements of austenitic stainless steel and the ceramic stabilizer (MgO) as well as the technological parameters lead to a significant change in the phase composition of the Mg‐PSZ. The changes can be analysed by EBSD due to the high spatial resolution.

No abstract

No abstract

Metal-matrix composite materials composed of an austenitic stainless steel with different ceramic particle reinforcements were investigated in this study. The test specimens were prepared via a powder metallurgical processing route with extrusion at room temperature. As reinforcement phase, either magnesia partially stabilized zirconia or aluminium titanate with a volume content of 5% or 10% was used. The mechanical properties were determined by quasi-static compressive and tensile loading tests at ambient temperature. The microstructure characteristics and failure mechanisms during deformation contributing to significant changes in strength and ductility were characterized by scanning electron microscopy including energy dispersive X-ray spectroscopy and electron back-scatter diffraction, and by X-ray diffraction. The composite materials showed higher stress over a wide range of strain. Essentially, the deformation-induced formation of α′-martensite in the steel matrices is responsible for the pronounced strain hardening. At higher degrees of deformation, the material behavior of the composites was controlled by arising damage evolution initiated by particle/matrix interface debonding and particle fracture. The particle reinforcement effects of zirconia and aluminium titanate were mainly controlled by their influences on martensitic phase transformations and the metal/ceramic interfacial reactions, respectively. Thereby, the intergranular bonding strength and the toughness of the steel/ceramic interfaces were apparently higher in composite variants with aluminium titanate than in composites with magnesia partially stabilized zirconia particles.